The present invention is directed to moldings such as decorative trim strip products made from thermoplastic extrusions. More particularly, the present invention relates to a method of forming an end of an elongated decorative and protective trim strip particularly useful as a body side molding on an automotive vehicle.
Moldings or trim strips are commonly applied as decorative and protective elements attached to automotive body panels such as door panels. While it is known to mold elongated trim strips from thermoplastic materials, moldings used in the automotive industry are generally made by extrusion because extrusion processing is capable of high production rates with relatively low tooling costs as compared to injection or other molding processes. Extrusion processing, however, incurs a disadvantage in that lengths of extrudate must be cut to provide suitable lengths for use on an automotive vehicle. Thus, the ends of such lengths generally must be finished in order to provide a smooth tapering or contoured surface which is aesthetically appealing.
A variety of approaches has been used in an attempt to provide contoured and shaped ends on extrusion formed thermoplastic strips. One approach is to separately mold an end cap onto the end of a main extrusion center section. This approach, however, provides a noticeable joint line between the molded end section and the extruded center section which is often undesirable. This approach also requires a difficult color matching to provide similar appearance between the end section and the center section. Color matching is especially difficult when metal flake colorants have been used and a molded end section is provided onto an extruded center section. Extrusion tends to orient the metal flakes in the product which is not matched by the molded end section.
Another method of forming an end section is taught in U.S. Pat. No. 5,227,108, Jul. 13, 1993 to Reid, Jr. et al. for "Method of Forming Decorative Trim Strips". In accordance with the Reid method an extruded length of thermoplastic material is first made of a length substantially equal to the desired length of the decorative trim strip with a first longitudinally extending surface of the length being a front show face and a second longitudinally extending surface opposite the first surface being a back mounting surface. Material is removed inwardly from the second surface to create a cavity behind the first surface while leaving the show face generally undisturbed. Thereafter the end portion of the extruded length with the cavity formed therein is enclosed in a mold chamber with an interior surface having the desired end shape and thermoplastic material is injected into the formed cavity to fill the cavity and force the show face of the enclosed end portion into engagement with the interior surface of the mold.
The Reid method provides an excellent method of forming contoured ends on extruded plastic strips by combining material removal and injection molding operations. The Reid method provides end portions without internal stresses and, within reason, the actual shape and contour provided on in portion can vary widely. The present invention is the nature of a further improvement of the method of the Reid, Jr. et al. patent. Thus, the present invention provides a molding having a light weight, hollow, body and which facilitates the material removal step. Furthermore, the present invention provides a "show face" or cover layer which is easily accurately dimensioned. Further understanding of the present invention will be had from the following disclosure taken in conjunction with the accompanying drawings.